The official ministerial briefing for the health and social care bill states some alarming statistics. Take these two statements drummed up by Number 10: "Someone in this country is twice as likely to die from a heart attack as someone in France" and "survival rates from cervical, colorectal and breast cancer are amongst the worst in the OECD". The purpose of these statistics is supposed to alarm the reader and justify changes to the NHS: the briefing being "that is why we need to modernise the NHS".

The first of these statements is probably based on the fact that in 2006, the age standardised mortality in the UK for acute myocardial infarction (heart attack) was 19/100,000 in France and 41/100,000 in the UK. The second has been widely reported. But interpreting official statistics needs care, and there are a few important principles to bear in mind:

1. One has to die of something

It doesn't really matter what. Deaths from any cause are the most reliable indicators of health experience. Life expectancy is a weighted average of death rates from all causes. For people aged 60, life expectancy is 22.5 years in the UK. This compares with 21.9 for Denmark, 23.0 for Germany , 23.9 for Spain and 24.5 for France. Thus at aged 60, the French can expect to live two years longer than us. The UK is not doing well but not as bad as perhaps the figures given in the briefing suggest.

Since heart disease is the major cause of death in both countries, how can one explain the difference in heart disease mortality rates? It could depend on how acute myocardial infarction is defined in the two countries. As discussed on Radio 4's More or Less on 21 January, there is some evidence that the French are less likely to ascribe sudden deaths to heart disease as other countries. You are twice as likely to be labelled as having died of a heart attack in the UK. The fact that you died of something else if you were French is scant consolation to your relatives.

2. Lifestyle is at least as important for determining differences in mortality rates as better medical care

This is reflected in the fact that the UK has lower death rates from lung cancer in men in 2008 than Spain, Demark, Italy France and Germany, possibly reflecting the successful anti-smoking campaigns in the UK. It is far better and cheaper to prevent disease than to cure it.

3. Survival rates depend not just on when you die but when you are diagnosed

Thus two people may both die at the age of 60 from breast cancer, but one was diagnosed at the age of 40 and the other at the age of 50. Thus the length of survival does not necessarily reflect better medical care but rather a better system for screening disease. Britain now has successful screening programmes for cervical, colorectal and breast cancer but these take time to take effect.

4. Always think about trends, not just a cross-sectional snapshot

After all, a photograph of a football match will not tell you who is winning. John Appleby, writing in this week's British Medical Journal points out that the UK standardised death rates for myocardial infarction have been declining at a faster rate than those of France, and are forecast to be lower by 2012. Similarly deaths from breast cancer are falling faster in the UK than in France and are forecast to be lower in a few years.

5. Correlation is not the same as causation

This is drummed into epidemiologists at an early age. There is a well-known positive correlation between the death rates in Victorian England and the proportion of church marriages, but that does not mean getting married in a church carries a higher risk. Thus the most egregious statement in the briefing is "That is why". There is no logical connection between the facts stated at the start of the briefing and the need for healthcare reform. There is not even a connection between the more reliable statistic of life expectancy and the need for healthcare reform.

It is not even clear that increased spending results in better medical care as an examination of the Quality and Outcomes Framework (QOF) demonstrates. A recent paper in the Annals of Family Medicine found little change in a number of indicators of quality of care for general practitioners from 2003 to 2007 during which the very expensive QOF programme was rolled out.